Isolation and identification of a black Aspergillus strain and the effect of its novel protease on the aroma of Moutai-flavoured liquor

摘要

Among Chinese traditional distilled liquors, Moutai-flavoured liquor is the most famous, owing to its complicated process as it is derived from fermented sorghum coupled with the use of a Moutai-flavoured Daqu. In this study, a novel isolate, belonging to a black Aspergillus, was obtained and identified as Aspergillus hennebergii by ITS-5.8S rRNA sequencing analysis and conventional morphologic identification. The influences of initial pH, carbon source, nitrogen source and metal ions on the production of an A. hennebergii protease were studied. The results revealed that metal ions exerted a significant effect on enzyme production and activity. Additionally, the potential application of the protease from A. hennebergii was investigated. The enzymatic hydrolysis resulted in the identification and quantification of 42 compounds, including alcohols, aldehydes, pyrazines and esters. These volatile compounds exhibited special flavour properties. Significant differences were observed between the enzyme treatments and the control sample. Samples from the enzyme treatments led to the highest amounts of alcohols, pyrazines and aromatics. These results suggest that A. hennebergii, or its protease, may have some application values for the enhancement of the quality of Chinese liquor and for the improvement of the liquor production process.